#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const ll mx=1e5+10;
const int mod= 1e9+7 ;
const ll inf=1e9+5;
//***while there is life there is hope
int n,m,k;
int siz[mx];
vector<int> adj[mx];
int arr[mx];
map<pair<int,int>,int>blocked;
int visited[mx];
int dfs(int node,int par){
int zz=arr[node];
visited[node]=1;
for(auto it:adj[node]){
int aa=min(node,it);int bb=max(node,it);
int yes=blocked[{aa,bb}];
if(it==par||yes){continue;}else{
zz+=dfs(it,node);
}
}
return zz;
}
map<int,pair<int,int>>edge;
int main() {
cin>>n>>k;int sum2=0;
for(int i=1;i<=n;i++){
cin>>arr[i];sum2+=arr[i];
}
if(sum2<=k){cout<<0;return 0;}
for(int i=0;i<n-1;i++){
int a,b;cin>>a>>b;
int aa=min(a,b);int bb=max(a,b);
edge[i]={aa,bb};
adj[a].push_back(b);
adj[b].push_back(a);
}
if(n<=15){
int sum=0;int ans=n;
int z=n;
for(int i=1;i<(1<<z);i++){
memset(visited,0,sizeof(visited));
int tt=0;
for(int j=0;j<n;j++){
if((1<<j)&i){
tt++;
int a=edge[j].first;
int b=edge[j].second;
int aa=min(a,b);int bb=max(a,b);
blocked[{aa,bb}]=1;
// cout<<"test "<<a<<" "<<b<<endl;
}else{
int a=edge[j].first;
int b=edge[j].second;
int aa=min(a,b);int bb=max(a,b);
blocked[{aa,bb}]=0;
}
}
int okk=1;
for(int i=1;i<=n;i++){
if(visited[i]){continue;}else{
int summ=dfs(i,0);
if(summ>k){okk=0;}
}
}
if(okk){
ans=min(ans,tt);
}
}
cout<<ans;}else{
int sum=0;int ans=0;
for(int i=1;i<=n;i++){
sum+=arr[i];
if(sum>k){sum=arr[i];ans++;}
}
cout<<ans;
}
}
